Wireless networks are composed of devices locally generating data for remote destinations. Wireless nodes typically use wireless communication (e.g., radio transmission) to send their data to a central computer system, which accumulates the data and builds it into a larger picture. In some wireless network systems, communication among nodes is organized as a set of links, scheduled in time into a communications superframe. A communications scheme organized in this way saves power by minimizing the total time each node needs to have its transmitter and receiver powered on. Each superframe can be designed for a different communication need (e.g., system startup, normal operation, node diagnostics, emergency purposes), and nodes can individually switch among superframes as necessary or nodes can have multiple superframes operating concurrently.
Data and control packets flow in wireless networks over graphs that locally route packets from node to node. Wireless nodes have finite output power and hence are limited to a certain communication range. Communication across the network from source to destination may require several retransmissions of the packet. Each transmission is called a hop, and each hop passes the packet from a sender node to a receiver node. Each unordered node pair between which it is possible to exchange packets in a network is called a path. A routing graph instructs the packet which paths are valid for the next hop of its route.
The fraction of packets transmitted by the sender that are properly received by the receiver and acknowledged on a path is called the path stability. To ensure adequate levels of performance, diagnostics are kept to quantify path stability throughout the network. The only way to certainly measure path stability is to send packets and see what fraction is acknowledged. Wireless performance on paths varies with time so it is expected that path stability changes and frequent packet sending is required to maintain an up-to-date measure of path stability.
Some paths are on high-traffic graphs which allow normal network functionality to generate enough data to measure path stability. Other paths, maybe to save power, are not used as frequently. Some paths also are used primarily for packet types that are not acknowledged and hence do not provide a mechanism for path stability measurement.